Agronomy •  2021-07-19

Controlling Western Bean Cutworm in Dry Beans

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Growers who follow Integrated Pest Management (IPM) best practices identify pests, monitor their levels and choose the most targeted products to manage them. For Canadian dry bean growers looking to maximize crop quality and yield across every acre, Western Bean Cutworm (WBC) can be a pest they face.

Western bean cutworm in dry beans

Known as a primary pest in corn, WBC was first detected in Ontario in 2008. A few years later, in 2014, WBC  spread to dry beans and this pest is now found in most dry bean growing areas in the province1.

After the late-tassel stage in corn, WBC moths seek out dry beans and lay their eggs deep in the crop canopy of dry bean fields anytime between mid-June and the end of August. However, because the larvae hide in the soil during the day before feeding at night, WBC is particularly hard for growers to scout before damage occurs.

Pheromone traps can be used to monitor moth activity and detect when peak flight occurs, with trap counts being especially important in identifying at risk fields and when scouting is required1. OMAFRA’s 2020 Dry Edible Bean Summary revealed that the number of WBC caught in pheromone traps was much higher in 2020 than in 2019 and they encourage growers to continue to trap moths on their fields so that insecticide applications can be targeted from 10 to 20 days after peak flight.

As scouting for egg masses in dry beans can be difficult, especially post-hatch, an alternative to egg and larval counts is to scout dry bean fields for pod feeding after peak moth flight, at multiple locations in a field2. However, this may still underestimate the damage being done.

Yield loss from direct bean feeding is not the major concern of WBC in dry beans - quality loss is. The feeding larvae allow for the introduction of pathogens and other insects to enter and cause further damage, reducing the crop’s marketable yield3. Due to this, it’s important for growers to have an insecticide within their IPM program, such as protecting dry beans from WBC with Intrepid™ insecticide.

Intrepid™ insecticide

Providing performance and peace of mind, Intrepid has both ovicidal and larvicidal activity. Ingestion is the main source of activity on pests, causing larvae to stop feeding within 24 hours of contact and providing long residual control for 10 to 14 days after application.

Intrepid also uses a novel mode of action, acting as a Molt Accelerating Compound (MAC), to specifically target lepidopterous pests like WBC. It does not adversely affect beneficial insects such as bees, predators and parasitoids, making it ideal for a sound IPM program.

For the best control of WBC in dry beans with Intrepid, follow these application best practices:

  • Apply Intrepid at the rate of 0.6 L per hectare in sufficient water volume; a minimum of 300 litres of water per hectare is recommended for ground application for complete coverage of the plant foliage
  • Applications should be timed at egg hatch or to small larvae
  • Repeat applications based on monitoring of insect populations
  • Apply a maximum of 3 applications per year
  • Do not apply within 7 days of harvest
  • Always read and follow label directions

To ensure crops are protected for the most quality, yield and profit at harvest, contact our horticultural experts about controlling Western bean cutworm in dry beans with Intrepid insecticide.